This page is about combining words and letters into longer words. For other uses, see Definition:Concatenation.
Let $\mathcal A$ be an alphabet of symbols.
Concatenation is the process of placing elements of $\mathcal A$ and words in $\mathcal A$ next to each other to form a longer word.
Let $a, b, c \in \mathcal A$.
Then concatenating $b$ to $a$ results in the word $ab$, and concatenating $c$ gives the word $abc$. Concatenating $b$ then gives $abcb$.
Concatenating $aba$ to $aabcba$ gives the word $aabcbaaba$.
The word concatenation derives from the Latin word catena for chain.
However, the end result of such an operation is not to be confused with a (set theoretical) chain.